A simple iterative power control scheme for successive interference cancellation

Abstract

Successive interference cancellation (SIC) is a technique which has the potential to increase the capacity of DS-CDMA systems substantially. One of the major criticisms of the technique is that it requires a specific distribution of unequal received powers from the mobile units. In the presence of estimation error, the required distribution becomes even more complicated and it is critical that the users adapt to these required power levels in order to achieve good system performance. In this paper, a simple iterative technique based on the existing power control algorithm for commercial CDMA systems is presented. This algorithm is shown to converge to the optimal power control solution for SIC, mathematically for a static channel, and with simulations for a fading channel. Convergence is considered as a function of important system parameters such as estimation error, power control step size, Doppler frequency, and the number of users in the system. The surprising conclusion is that power control for a realistic successive interference cancellation system doesn't require additional complexity relative to a conventional CDMA system.